Electrostatic power amplifier tubes having an improved positioning of the control electrode



May 20, 1969 v J. E. OLSON 3,445,711

ELECTROSTATIC POWER AMPLIFIER TUBES HAVING AN IMPROVED POSITIONING OF'THE CONTROL ELECTRODE Filed Oct. 26. 1966 fl'igf] :UQC EEG:

IN VEN TOR.

Jar/r [bu 4R0 0160 BY W ' ATTORNEY Patented May 20, 1969 ELECTROSTATIC POWER AMPLIFIER TUBES HAVING AN IMPROVED POSITIONING OF THE CONTROL ELECTRODE Jack Edward Olson, Lakewood, Colo., assignor to Trueline Instruments, Inc., Englewood, Colo., a corporation of Colorado Filed Oct. 26, 1966, Ser. No. 589,565 Int. Cl. H01j1/00, 19/14 US. Cl. 313-438 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an electron tube and more particularly to an electrode structure for electron tubes. The invention has for its principal object the provision of a rugged electron tube for use in matching a low impedance circuit to an ultra high impedance circuit to produce an accurate and relatively large power amplification of the frequencies of the high impedance circuit for any desired purpose without introducing disturbances, distortions or current losses in either circuit.

The usual triode type of electronic tube comprises an evacuated tube or envelope containing: a heated cathode for emitting electrons, a plate for collecting electrons emitted by the cathode; and a grid or control element positioned in the interelectrode space between the cathode and the plate for electrostatically controlling the flow of electrons from the cathode to the plate.

This conventional positioning of the control element intermediate the electron emitter and the collector produces many objectionable results. For instance, the control element is positioned directly in the electron stream so that it tends to draw extraneous current from the stream resulting in negative feedback, amplification loss, loading of the input circuit and other inaccuracies and distortions.

Another objection is the difficulty in producing uni-form interchangeable tubes on an assembly line basis since minute variations in the forming of the spacing of the elements will result in variations in the space charge and variations in the degree of immersion of the control element in the electron stream, all of which tend to produce a non-uniform and undesirable output.

Briefly, the present invention avoids the above objectionable results by completely removing the control element (grid) from the interelectrode space and out of the electron stream and positioning it on the opposite side of the collector (plate) so it will be physically and electrostatically shielded from the electron stream by the collector and by providing one or more accurately predesigned force field passages or openings through which the negative repusion charges of the control element will be transmitted to the space charge rising from the cathode to the dimensions and configuration of the space charge and the degree of immersion of the collector therein. This places the control element completely outside of the electron current stream so that it will draw no current from the stream and yet will supply accurate, highly-efiicient electrostatic control thereover regardless of mechanical misplacements.

The net result of the new placement of the control element and the specific force field passages is that any current loss from the emitting element to the control element is extremely low. In fact, the loss will usually be limited to the volume resistivity of the glass or other insulating material supporting the electrodes.

Other objects and advantages reside in the detail con struction of the invention, which is designed for simplicity, economy, and efficiency. These will become more apparent from the following description.

In the following detailed description of the invention, reference is made to the accompanying drawing which forms a part hereof. Like numerals refer to like parts in all views of the drawing and throughout the description.

In the drawing:

FIG. 1 is a diagrammatic, perspective, broken-away, view showing the essential elements of a preferred simplified form of the present invention;

FIG. 2 is a suggested schematic symbol for the form illustrated in FIG. 1;

FIG. 3 is a diagrammatic, broken-away perspective view of the elements of an alternate form of the invention;

FIG. 4 is a suggested schematic symbol for the alternate form of FIG. 3; and

FIG. 5 is a detail perspective view of a cathode element as employed in the form of FIG. 1 to be later described.

The simple form of the improved tube, as shown in FIG. 1 is assembled in a cylindrical, highly evacuated, glass or electrically insulated metal shell 10 having a sealed, relatively flat, insulated, base 11 at its bottom and a sealed, concentric, terminal nipple 12 at its top. A metallic, preferably pointed, needle, which will be herein designated as the control element 13, is sealed in the nipple 12 and extends axially downward into the interior of the shell 10 at its lower extremity and upwardly therefrom to a circuit contact thimble 14 as its upper extremity.

A horizontal, relatively thin, metallic, circular, collector plate (anode) 15, which may be fiat 0r shaped to conform with either the geometry of the space charge arising from the cathode or so as to produce special amplification characteristics, is concentrically supported in the shell about the lower extremity of the control element 13 upon a metallic leg 16 which is sealed in and extends downwardly through the base 11 to either form or be attached to an electrical contact pin 17. A circular force field opening 18 is centrally formed in the collector plate 15 and concentrically surrounds the axis of the control element 13 at or slightly below the pointed lower extremity of the latter.

An inverted hollow cathode cup 19 (as shown in FIG. 5) having a closed top and open bottom is concentrically supported in the shell below the collector plate 15 upon a metallic supporting post 20 which is sealed in and extends downwardly through the base 11 to form an input pin 21 thereon. The top of the cathode is formed of or coated with suitable cathodic material. The downwardly extending sides of the cathode cup, indicated at 19', need not be cathodic.

A helically or spirally wound filament 22 of suitable resistance wire is axially positioned within, but out of contact with, the cathode cup 19. The terminals of the filament 22 are connected to filament pins 23 and 24 sealed in and extending downwardly from the base 11.

In actual practice an electron tube having a collector plate .6" diameter with a force field opening .02" in diameter, positioned .064" above a cathode cup .25" in diameter was found to function very satisfactorily. In fact, a signal power gain in the order of was accomplished with the latter tube structure.

In use, the improved tube functions similarly to the usual triode. That is, the negative charged cathode cup 19, is heated by the filament 22 so as to emit a somewhat flat space charge which impinges upon the collector (plate) 15 without interference from an intervening grid element such as encountered in the common triode. The collector plate 15 may be positively biased to increase the current flow between emitter and collector through the external circuit or to electrically control or alter the tubes operational characteristics. This positive bias which may be placed upon the collector plate (in respect to the cathode) may be thought as increasing the involvement of the collector plate in the space charge by altering its (space charge) potential gradient and geometry. However, a negative charge in the control element 13 reacts through the force field opening 18 to compress the space charge in the interelectrode space between the plate 15 and cathode 19 thereby reducing the involvement of the control element in the space charge and the conventional resulting loss of current in the external circuit between the collector plate and the cathode.

The alternate form shown in FIGS. 3 and 4 is based on the same principle of operation. That is, the control element is positioned exteriorally of the intervening space between the cathode and collector (plate) so as to remove the possibility of physical and electronic contact between the electron stream and the control element.

The alternate form of the improved power triode is assembled in a glass shell having a sealed bottom 26, similar to the shell 10 of the preceding form and comprises an elongated, cylindrical cathode tube 27 supported on a cathode post 28 extending through bottom 26 and terminating in or connected to a cathode pin 29. The cathode tube 27 surrounds an elongated heater or filament 30 which is electrically connected to filament pins 31 and 32 on the bottom 26. A plurality of similar, parallel, relatively narrow, open, cylindrical collector rings 33 concentrically surround the cathode tube 27 in radially-spaced relation thereto. The collector rings 33 are axially and uniformly spaced apart along the cathode tube 27 so as to leave uniform intervening spaces therebetween and are supported in any suitable manner such as by metallic arms 34 extending from a vertical supporting and conducting leg 35 which extends downwardly through the bottom 26 to form or connect with an output pin 36.

An annular, relatively thin, fiat, metallic, repellor disc 37 is medially positioned in each intervening space between adjacent collector rings 33 in a plane parallel to the planes of the rings. The repellor discs 37 have a larger outer diameter than the collector rings 33 and each is provided with a concentric inner opening 38 substantially equal in diameter to the diameter of the collector rings 33. The repellor discs 37 are medially supported between the collector rings 33 by means of a metallic post 39 extending downwardly through the bottom 26 to form or close contact with a grid pin 40 in the bottom 26.

The operation of the alternate form of FIG. 3 is similar to that described with reference to FIG. 1. The interelectrode paths between the cathode tube 27 and the collector rings 33 are mechanically free and clear of any control elements. The negative charges from the repellor discs 37 remotely and externally effect the interelectrode space charge from the outside of the electron path through the openings 38 and the spaces between the collector rings 33 similarly to the negative charges through the force field opening 18 of the previously described form.

While specific forms of the invention have been described and illustrated herein, it is to be understood that the same may be varied within the scope of the appended claims, without departing from the spirit of the invention.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. An electrode structure for evacuated electron tubes comprising:

(a) a cathode element;

(b) means for heating said cathode element to emit electrons therefrom; (c) an electron collector element positioned to receive a stream of electrons from the heated cathode; and

(d) an electronic control element positioned within said tube adjacent said stream of electrons and exteriorally of the path of said electron stream, said electron collector element being concentrically aligned with the cathode and positioned between said cathode and said control element with said collector element having a concentrically positioned force field opening therein, whereby a variable polarity voltage may be impressed on said control element to correspondingly control the flow of electrons between said cathode and collector elements.

2. An electronic structure as described in claim 1 in which the control element comprises an elongated electrode axially aligned with said force field opening on the side of said electron collecting element distant from the interelectrode space between said cathode and said collecting element.

3. An electronic structure as described in claim 2 in which the extremity of said control element adjacent said collecting element terminates in a relatively sharp point.

4. An electronic structure as described in claim 2 in which the cathode comprises a cylindrical metallic ring and the collecting element comprises an annular relatively fiat metallic plate having said force field opening concentrically positioned therein.

5. An electronic structure as described in claim 4 having a plurality of said collecting elements axially aligned with said cathode in spaced-apart relation and a plurality of control elements each of said latter elements being positioned in the intervening space between two adjacent collecting elements.

References Cited UNITED STATES PATENTS 9/1928 Cohn 313308 2/1936 Parker 313293 US. Cl. X.R. 

